The present invention relates generally to regulation circuits. More specifically, the present invention relates to a high performance regulation circuit load are that is fully integrated onto a single CMOS integrated circuit with a circuit load.
The demand for smaller and faster electronic devices has increased the demand for integrated circuitry. This results in a greater use of digital components in the integrated circuit's load. Unfortunately, the use of digital circuitry may produce circuit noise that can affect the performance of the integrated circuit. Examples of such circuits are mixed-mode circuits, analog circuitry along with digital circuits, and large digital circuits that generate a lot of noise. In order to reduce this concern with integrated circuitry, regulation circuits have been used.
An example of an integrated mixed-mode circuit that requires regulation is a broadband tuner. Broadband tuners are integrated into a wide range of consumer electronics, ranging from familiar household standards, such as televisions and VCRs to newer more complex devices including cable settop boxes, cable modems, cable telephony systems, web TVs, PC/TV and the various implementations of digital television. Functioning as the RF broadband gateway, the basic function of a tuner in these devices is to receive all available channels in the input bandwidth, select a desired channel and reject all others and translate the desired channel to a standard intermediate frequency (IF). These tuners operate over a frequency range of 50-860 MHz, taking into consideration those frequencies used by broadcast television and cable operators.
Tuners that enable products to support PC, TV and internet functionality have very different performance requirements than the traditional television tuner. As applications become more sophisticated, tuners with higher performance are required. Tuners are increasingly being required to be fully integrated into a single integrated circuit. However, the performance of existing integrated tuners is limited by the phase noise of a fully integrated oscillator within the broadband tuner. To improve the performance of the tuner, a lower phase noise fully integrated oscillator is used.
Also used to improve the performance of the single integrated circuit tuner is a low noise amplifier combined with a voltage controlled oscillator (VCO) and frequency synthesizer onto the common integrated circuit substrate. In order to implement this combination, systems have employed current steering logic for the synthesizer frequency dividers. This is done to minimize the frequency disturbance (spurs) generated by the dividers and prevent them from interfering with the low noise amplifier when the low noise amplifier, frequency dividers, and other sensitive analog circuitry are integrated onto a common substrate. Unfortunately, current steering frequency dividers have high phase noise and severely limit the phase noise performance achievable for an integrated VCO.
Accordingly, there is a need for a regulation circuit that can be combined with a circuit load on a single integrated circuit substrate, which prevents substrate disturbances generated by the circuit load from interfering with the output.
There is also a need for a fully integrated tuner which combines low noise broadband radio frequency amplifiers with very low phase noise digital frequency synthesizer dividers on a single integrated circuit substrate and which prevents the frequency disturbances generated by these digital dividers from interfering with the broadband low noise amplifier.